Muhammad Maqbool

Effect of phase transition on the optoelectronic properties of Zn1−xMgxS

Density functional calculations are performed to investigate the structural, electronic, and optical properties of Zn1−xMgxS (0u2009≤u2009xu2009≤u20091). In the present DFT calculations, we used modified Becke-Johnson potential in the exchange and correlation energy, which is effective for the treatment of the d-orbitals. A structural phase transition from zinc-blende to rock-salt is observed at 73% magnesium, which is consistent with the experimental results. Furthermore, the alloy has direct band gap nature for the whole range of Mg concentration in the zinc-blende structure, while the band gap nature for the rock-salt phase is indirect. The zinc-blende crystal structure has many established applications in the UV optoelectronic devices, and therefore the maintenance of the compound in zinc-blende crystal structure for the maximum range of Mg-composition is highly desirable which is dependent on the composition rate, external environment, and thickness of the film. Keeping in view the importance of ZnMgS in UV optical ...

Spectroscopy of gadolinium ion and disadvantages of gadolinium impurity in tissue compensators and collimators, used in radiation treatment planning

Intense ultraviolet emission from gadolinium doped amorphous aluminum nitride thin films deposited on Si (111) substrate is studied with cathodoluminescence and photoluminescence. The purpose of the study is to find the merits or demerits of gadolinium ions if added intentionally or present as unintentionally added impurity in tissue compensators or collimators in radiation treatment planning. These films are deposited by reactive sputtering at liquid nitrogen temperature, using 100- 200 W RF power, 5-8 mTorr nitrogen, and a metal target of aluminum and gadolinium. Thermal annealing was performed at a temperature of 900 ◦ C. A sharp ultraviolet peak is observed at 314 nm corresponding to 6 P7/2 → 8 S7/2 transition. The ultraviolet emission is intense enough to harm human tissues if it is used as tissue compensator. Intense ultraviolet emission is observable even if the concentration of gadolinium is less than 0.5%. Thermal annealing further enhances the intensity of ultraviolet emission, indicating that longer use of such tissue compensators or collimators containing gadolinium ions will provide more harm and damage to human body. Radiation Therapists, Oncologist and industries making tissue compensators and collimators are strongly suggested to test any compensator or collimator for gadolinium impurities.

Intriguing electronic structures and optical properties of two-dimensional van der Waals heterostructures of Zr2CT2 (T = O, F) with MoSe2 and WSe2

Based on (hybrid) first-principles calculations, material properties (structural, electronic, vibrational, optical, and photocatalytic) of van der Waals heterostructures and their corresponding monolayers (transition metal dichalcogenides and MXenes) are investigated. MoSe2/Zr2CO2 and WSe2/Zr2CO2 heterostructures are found to be indirect band gap semiconductors with type-I and type-II band alignment, respectively, while MoSe2/Zr2CF2 and WSe2/Zr2CF2 are metals. A transition from type-I to type-II band alignment is achieved in MoSe2/Zr2CO2 by moderate compressive and tensile strain. Furthermore, absorption spectra are calculated to understand the optical behavior of these systems, whereas red and blue shifts are observed in the positions of the excitonic peaks under tensile and compressive strain in the heterostructures. Photocatalytic studies show that MoSe2/Zr2CO2 and WSe2/Zr2CO2 heterostructures can oxidize H2O/O2 to O2, but unlike their parent monolayers (MoSe2, WSe2 and Zr2CO2) these heterostructures fail to reduce H+ to H2.

Toxicity of PEG-Coated CoFe 2 O 4 Nanoparticles with Treatment Effect of Curcumin

In this work, CoFe2O4 nanoparticles coated with polyethylene glycol (PEG) were successfully synthesized via a hydrothermal technique. Morphological studies of the samples confirmed the formation of polycrystalline pure-phase PEG-CoFe2O4 nanoparticles with sizes of about 24xa0nm. Toxicity induced by CoFe2O4 nanoparticles was investigated, and biological assays were performed to check the toxicity effects of CoFe2O4 nanoparticles. Moreover, the healing effect of toxicity induced in living organisms was studied using curcumin and it was found that biochemical indexes detoxified and improved to reach its normal level after curcumin administration. Thus, PEG-coated CoFe2O4 synthesized through a hydrothermal method can be utilized in biomedical applications and curcumin, which is a natural chemical with no side effects, can be used for the treatment of toxicity induced by the nanoparticles in living organisms.

Klein-Nishina electronic cross-section, Compton cross sections, and buildup factor of wax for radiation shielding and protection

Klein-Nishina scattering cross-sections, Compton scattering, mass attenuation and energy transfer cross-sections, linear attenuation coefficient and buildup factor of 99.99% pure paraffin wax (Carbonxa0=xa085.14%, Hydrogenxa0=xa014.86%). are calculated using 0.662, 0.835, 1.17 and 1.33 MeV γ-rays. The mentioned γ-rays were obtained from Cs-137, Mn-54 and Co-60 radioisotopes. Gamma rays obtained from these radioisotopes were passed through circular shaped wax slices and allowed to fall on a NaI detector. The thickness of wax slices were 0.33-2.9 cm with 6 cm diameter. Lead collimator of 1 cm diameter hole in the middle was used to obtain a collimated beam for narrow beam geometry. Broad beam geometry was used by removing the collimator to investigate buildup factor. Results show that Klein-Nishina electronic cross-section, Compton mass attenuation coefficient and Compton energy transfer coefficient all decrease with increasing photon energy. Linear attenuation coefficients μxa0=xa00.0532 cm-1 for 1.17 MeV beam and μxa0=xa00.0419 cm-1 for 1.33 MeV γ-rays were obtained for wax. Variations in buildup factors are observed with increasing thickness of wax for 1.17 and 1.33 MeV beams.

Nuclear Medicine Physics

Nuclear medicine physics is a subspecialty of medical physics. Nuclear medicine practice includes diagnostic procedures of imaging and non-imaging and radionuclide therapy protocols primarily for cancer treatment. Nuclear medicine physics is to apply physics principles and technology to support clinical nuclear medicine. Nuclear medicine is a branch of physics that utilizes nuclear technology for the diagnosis and treatment of diseases. It covers radionuclide production, interaction, detection, and imaging. It also involves radiation dosimetry and radionuclide therapy procedures.

Interaction of Gamma Rays and X-Rays with Matter

Gamma rays are electromagnetic radiation either emitted from a nucleus or an annihilation reaction between matter and antimatter. X-rays are electromagnetic radiation emitted by charged particles (usually electrons) in changing atomic energy levels or in slowing down in a Coulomb force field. X-rays and gamma rays have identical properties, only differing in their origin. The two used to be distinguishable by energy of the particle, but now linear accelerators are able to produce high-energy X-rays that have the same or higher energy as gamma rays. The practical range of photon energies emitted by radioactive atoms extends from a few thousand eV up to over 7 MeV. On the other hand, linear accelerators are able to produce more energetic photons. The energy ranges of X-rays in terms of generating voltage are given in Table 3.1.

Basic Concepts in Radiation Dosimetry

Directly and indirectly ionizing radiations deposit their energy in a medium while passing through it. Radiation dosimetry is a procedure that deals with the methods for quantitative determination of that deposited energy. To be more specific, quantitative determination of energy absorbed in a given medium by directly or indirectly ionizing radiations is called radiation dosimetry. It plays a crucial role in radiation therapy, nuclear medicine and radiation protection. Due to its significance, accurate determination of the deposited energy (often termed a radiation absorbed dose) at the point of interest in the medium (i.e., human body or phantom) is needed. A number of quantities and units have been defined for describing the radiation beam, which ultimately leads to the determination of radiation absorbed dose to the medium by incident radiation. These quantities and units are explained in this chapter. Furthermore it covers the fundamental ideas and principles involved in radiation dosimetry.